Computational methods for free surface flow
In physics, a free surface flow is the surface of a fluid flowing that is subjected to both zero perpendicular normal stress and parallel shear stress. This can be the boundary between two homogeneous fluids, like water in an open container and the air in the Earth's atmosphere that form a boundary at the open face of the container.
Source: Wikipedia — Computational methods for free surface flow (CC BY-SA 4.0)